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一、问题的提出哈尔滨标准件厂在加工低碳钢(ML—15)M20螺母时,一直采用碳素工具钢丝锥,转速为82.5转/分(V=5.2米/分),切削液为5％乳化液。在加工时出现丝锥耐用度严重降低的问题,每支丝锥平均加工三、四十个螺母。螺纹表面光洁度甚低,精度也不合格。还常常发生扭断丝锥的现象。螺母毛坯经退火后的金相组织为粗大的铁素体,性质又软又粘(其HRB50,σ_b=50公斤/毫米~2,延伸率δ=38～40％),造成了攻丝的困难。
First, the problem raised Harbin Standard Parts Factory in the processing of low carbon steel (ML-15) M20 nut, carbon tool steel tap has been used, the speed of 82.5 rev / min (V = 5.2 m / min), cutting fluid 5 % Emulsion. Taps in the processing of a serious decline in the durability of the problem, the average processing of each tap thirty or forty nuts. Thread surface finish is very low, the accuracy is not qualified. Torn tap often also occur. The annealed microstructure of the nut blank is coarse ferrite, soft and sticky in nature (its HRB50, σ_b = 50 kg / mm 2, elongation δ = 38-40%), resulting in the difficulty of tapping .